1. Field of the Invention
This invention relates to a bushing seal for a rotary member such as a centrifugal compressor. More particularly, this invention relates to a bushing seal with means for keeping the bushing surfaces wet wherever a process gas may come in contact with the bushing surfaces.
2. Description of the Prior Art
The present invention has particular adaptation for compressors for wet chlorine gas. In the production of chlorine, chlorine gas is generated on electrolytic cells. Where chlorine gas is collected, it is near atmospheric pressure. The collected chlorine gas is saturated with water and has an elevated temperature. Before the chlorine gas is compressed, the gas from the electrolytic cells is passed through a heat exchanger and moisture separator. Historically, the apparatus for heat exchange and moisture separation was the process capacity limit related to the volume of the chlorine gas passed through the equipment. With the advent of compressing the chlorine gas prior to passing it through the heat exchanger and moisture separator, the wet chlorine gas presented numerous problems relative to corrosion to metals commonly used in the manufacture of the compressors and its seals. One metal which resists the corrosive tendencies of wet chlorine gas is titanium.
Titanium, while resistant to corrosion from wet chlorine, is highly reactive with dry chlorine. If chlorine was to contact dry titanium, the chlorine and titanium react violently in an exothermic reaction until either the chlorine or the titanium is completely consumed by the reaction. Due to this reaction between titanium and dry chlorine, a special effort was made to keep the many titanium parts of the compressor and rotary shaft seal wet. Accordingly, prior art compressors for chlorine gas used carbon ring seals which were steam buffered. A disadvantage of carbon ring seals is that they wear and require frequent maintenance because it is impossible to keep their many parts wet. While, it would be desirable to have a long wearing seal such as a pumping buffered bushing seal as disclosed in commonly assigned U.S. Pat. No. 3,724,861, such a seal has too low an inner leakage and, with chlorine having a high affinity with water, could result in chlorine escaping to the atmosphere.